Choose a specific neural synapse in the body and describe in detail all the even
ID: 3513032 • Letter: C
Question
Choose a specific neural synapse in the body and describe in detail all the events that occur when one neuron communicates with another. Begin with an action potential arriving at an axon terminal. End with an excitatory post-synaptic potential. Be sure to include, name and describe the movements of specific chemicals, ions, changes in membrane potential, and the activities of specific membrane proteins. Explain how the excitatory event is stopped. Your answer must be written as an essay (complete sentences with a logical organization).Explanation / Answer
The synapse
How neurons communicate with each other at synapses. Chemical vs. electrical synapses.
Communication of neural synapse:
A single neuron, or nerve cell, can do a lot! It can maintain a resting potential—voltage across the membrane. It can fire nerve impulses, or action potentials. And it can carry out the metabolic processes required to stay alive.
A neuron’s signaling, however, is much more exciting—no pun intended!—when we consider its interactions with other neurons. Individual neurons make connections to target neurons and stimulate or inhibit their activity, forming circuits that can process incoming information and carry out a response.
How do neurons "talk" to one another The action happens at the synapse, the point of communication between two neurons or between a neuron and a target cell, like a muscle or a gland. At the synapse, the firing of an action potential in one neuron—the presynaptic, or sending, neuron—causes the transmission of a signal to another neuron—the postsynaptic, or receiving, neuron—making the postsynaptic neuron either more or less likely to fire its own action potential.
Overview of transmission at chemical synapses:
Chemical transmission involves release of chemical messengers known as neurotransmitters. Neurotransmitters carry information from the pre-synaptic—sending—neuron to the post-synaptic—receiving—cell.
As you may remember from the article on neuron structure and function, synapses are usually formed between nerve terminals—axon terminals—on the sending neuron and the cell body or de
A single axon can have multiple branches, allowing it to make synapses on various postsynaptic cells. Similarly, a single neuron can receive thousands of synaptic inputs from many different presynaptic—sending—neurons.
Inside the axon terminal of a sending cell are many synaptic vesicles. These are membrane-bound spheres filled with neurotransmitter molecules. There is a small gap between the axon terminal of the presynaptic neuron and the membrane of the postsynaptic cell, and this gap is called the synaptic cleft.
When an action potential, or nerve impulse, arrives at the axon terminal, it activates voltage-gated calcium channels in the cell membrane. ext{Ca}^{2+}Ca2+C, a, start superscript, 2, plus, end superscript, which is present at a much higher concentration outside the neuron than inside, rushes into the cell. The ext{Ca}^{2+}Ca2+C, a, start superscript, 2, plus, end superscript allows synaptic vesicles to fuse with the axon terminal membrane, releasing neurotransmitter into the synaptic cleft.
The molecules of neurotransmitter diffuse across the synaptic cleft and bind to receptor proteins on the postsynaptic cell. Activation of postsynaptic receptors leads to the opening or closing of ion channels in the cell membrane. This may be depolarizing—make the inside of the cell more positive—or hyperpolarizing—make the inside of the cell more negative—depending on the ions involved.
In some cases, these effects on channel behavior are direct: the receptor is a ligand-gated ion channel, as in the diagram above. In other cases, the receptor is not an ion channel itself but activates ion channels through a signaling pathway
Chemical synapses are flexible
If you've learned about action potentials, you may remember that the action potential is an all-or-none response. That is, it either happens at its full strength, or it doesn't happen at all.
Synaptic signaling, on the other hand, is much more flexible. For instance, a sending neuron can "dial up" or "dial down" the amount of neurotransmitter it releases in response to the arrival of an action potential. Similarly, a receiving cell can alter the number of receptors it puts on its membrane and how readily it responds to activation of those receptors. These changes can strengthen or weaken communication at a particular synapse.
Presynaptic and postsynaptic cells can dynamically change their signaling behavior based on their internal state or the cues they receive from other cells. This type of plasticity, or capacity for change, makes the synapse a key site for altering neural circuit strength and plays a role in learning and memory. Synaptic plasticity is also involved in addiction.
In addition, different presynaptic and postsynaptic cells produce different neurotransmitters and neurotransmitter receptors, with different interactions and different effects on the postsynaptic cell.